assume cs:code

code segment
start:	mov ah,0
	int 16h

	mov ah,1
	cmp al,'r'
	je red
	cmp al,'g'
	je green
	cmp al,'b'
	je blue
	jmp short sret

red:	shl ah,1
green:	shl ah,1

blue:	mov bx,0b800h
	mov es,bx
	mov bx,1
	mov cx,2000
s:	and byte ptr es:[bx],11111000b
	or es:[bx],ah
	add bx,2
	loop s

sret:	mov ax,4c00h
	int 21h
code ends
end start
